The present invention is broadly concerned with a pellet implant system which administers an antibiotic pellet subcutaneously along with a pharmaceutical pellet implant in a single combined procedure which provides controlled, sustained localized antibiotic release in order to prevent infections at the injection site. More particularly, it is concerned with an implanter having a pellet magazine containing antibiotic and pharmaceutical pellets with an associated injection needle, as well as structure permitting injection of pellets from the magazine through the needle for implantation under the skin of an animal. The magazine is loaded with antibiotic and pharmaceutical pellets for distribution in sequence singly or in multiples into the same injection site.
Implant technology, that is to say, procedures involving subcutaneous implant of pharmaceuticals and medical devices, is now well accepted and widespread in the areas of animal health and production enhancement as well as human health. Growth stimulants are commonly used to enhance the body weight of animals which are raised for slaughtering, such as cattle, swine, sheep, turkeys, chickens, and the like.
In the case of cattle, swine and sheep, approved growth stimulants are administered as solid pellets which are injected by an implanter equipped with a hypodermic needle. The needle is used to make a surface self-sealing and, non-coring implant receiving puncture beneath the skin of the ear of the animal. Small pellets of growth hormone are forced through the needle and left under the skin as the needle is removed from the ear. The ears are commonly discarded in slaughtering, such that no unabsorbed residues of such pellets will end up in food products intended for humans or domestic animals. The pharmaceutical in the pellets is normally formulated for timed release and continuous, sustained absorption of the active ingredients over an extended period of time.
Many types of pharmaceuticals such as bioactive compounds may also be implanted and include insulin, endocrine hormones for control of reproduction, vaccines, and biocides for flea and parasite control in humans, horses, and domestic animals such as dogs and cats. The compounds may be administered subcutaneously at any suitable location on the body.
Similar therapeutic procedures may be employed to implant drug delivery devices such as controlled release osmotic pumps in humans and animals as well as transponder devices in animals.
In the case of farm animals, the pellets are normally implanted while an animal is confined in a chute. An ear is grasped in one hand, and an implanter device having a large hypodermic needle is used to puncture the hide and subcutaneously inject a pellet dose into an implant receiving puncture. The implanting must be done carefully to insure that the pellets are properly placed and that no pellet remains extending from the puncture outside the hide. The procedure must be carried out quickly since the animals are not entirely cooperative and may shake their heads to free the held ear.
It is virtually impossible in such situations to provide a sterile injection site on a single animal or to prevent transfer of infective microbes from one animal to the next on the injecting needle. Further complicating the matter is that other procedures may be occurring at the same time as the implanting operation while the animal is confined, such as ear tagging, branding, veterinary inspections or procedures, or the like, which may further excite the animal and make injecting and disinfecting difficult. It is not unusual to even have manure at the injection site.
U.S. Pat. No. 5,522,797 (hereinafter "the '797 patent"), and entitled Slide Action Veterinary Implanter, which patent is hereby incorporated by reference, discloses an implanter which employs a slide action mechanism to retract an impeller, store an impeller driving force in a spring in cooperation with a latch mechanism, reset a trigger, and advance a pellet magazine, all by a single trigger actuated reciprocation of the slide mechanism. Operation of the trigger also forces the pellets from the magazine through the needle and under the skin of the animal.
Efficient implanters such as that taught in the '797 patent permit rapid sequential injection of many animals in a single session, leaving each animal with an open implant receiving puncture at the site of each injection. The injections are administered at locations such as feedlots where skin heavily contaminated with bacteria is common. Following the procedure, the implant receiving puncture is not bandaged, leaving the puncture open to contamination caused by contact with other animals, structures or the ground and by migration across the skin.
Consequently, bacteria introduced into the implant site, either during the delivery of the implant or thereafter may cause an infection at the site. Such infections may and often do result in abscesses, which may reduce the effectiveness of the implant by encapsulation of the implant pellet or by pushing the therapeutic pellet out of the original insertion implant receiving puncture, thereby preventing absorption and transport of the active ingredients. It is estimated that from about 10% to about 15% of feedlot cattle which are implanted in the United States subsequently develop abscesses.
A variety of techniques are currently employed to reduce the incidence of abscesses. Implant manufacturers recommend disinfection of the implanting tool, pellet magazines and needles, and observation of good sanitation practices during the implantation process. The implantation site may be cleaned or disinfected prior to injection to help prevent entry of resident bacteria into the implant receiving puncture and the needle, which may be employed to inject dozens of animals, may be disinfected between animals to prevent the transfer of bacteria from one animal to the next.
In addition, attempts have been made to augment the formulation of the pharmaceutical pellets themselves with boric acid, and to dust the implants prior to sale with an antibacterial compound such as oxytetracycline.
While all such measures may serve to increase sanitation and to reduce initial contamination of the implant receiving puncture, they do not administer an effective and predetermined quantity of an antibacterial agent and do not provide sustained inhibition of bacterial growth inside the implant receiving puncture itself. Controlled, sustained release of an antibacterial agent is needed to combat both microorganisms which have been introduced during the implant process and later multiply and new bacteria which may later enter through the implant receiving puncture from the surface of the hide.
Previous sustained release antibiotics for ruminants such as disclosed by Chou in U.S. Pat. No. 4,066,754 have been administered orally in bolus form. Such antibiotic preparations are systemic, rather than localized in their effects, and they must be administered orally in a separate procedure from the pellet implantation disclosed in the '797 patent.
Accordingly, there is a need for an antibiotic or bacteriostatic pellet system which delivers subcutaneously both pharmaceutical and antibiotic or bacteriostatic pellets to provide sustained localized prevention of infections at the injection site, and which does so without causing any additional implant receiving punctures.